i played back in the day and know alot about what to do and what not to do in wow. i figured i would help if ya want it.
1) find a guild.
playing in a guild will allow you to successfully play feral/ret/shadow. if the guild doesnt understand this quit guild and find another who does. it also serves as a group finder and social platform for you to take part in.
2) do some research .
putting in a little time will only help you be successful. this is a must if you raid. learning mechanics about the game will leave you less clueless and will help you when you do pug to not do a faux pas.
3)be helpful to those around you.
if you are a priest and see someone struggling on a mob drop a fortitude and pop a few heals . youll make a friend for life sometimes.
4) keep a network of those who have treated you well or have rare enchants.
also keep track of assholes.
5) have fun.
dont keep doing something you dont enjoy . its not worth it in the long run.